1. Field
The present invention relates generally to the field of digital-to-analog converters (DACs), and more particularly to techniques for automatically calibrating the current switch elements of the DACs.
2. Description of Related Art
Demand for high speed and high resolution DACs continues to grow, driven primarily by strong growth in the markets for wired and wireless communications. In one high speed and high resolution DAC architecture, the DAC receives a digital input sequence which represents a desired output current, and the current source switch elements are selectively turned on and off to provide the desired output current. In order to provide a linear output current, the current source switch elements should each produce a matching current.
One problem that may potentially hamper the performance of the high speed and high resolution DAC is the current source switch element mismatch. To detect and/or correct the current source element mismatch, attempts have been made in the past to measure the output current at the source node of the current source switch element. However, because the source node current measurement does not necessarily reflect the mismatch caused by the current source switch element and the associated weighting network, the source node calibration method fails to address the mismatch problem fully. A better position to take output current measurement may be the output node of the DAC, although it is generally difficult to separate the target current source switch element from the other current source switch elements.
Thus, there is a need for a DAC calibration system that measures and corrects the mismatch of the current source switch elements at the output node of the DAC.